The paper addresses four major "grades" of postconsumer recovered paper: old corrugated containers, office papers (computer printout, white ledger, and sorted office paper), mixed paper, and old newspapers. The definitions for these paper grades are as follows:

Old Corrugated Containers (OCC)

Used cardboard boxes.

Office Papers

Computer Printout (CPO). White, groundwood-free papers used for printing computer-generated data. Typically are continuous, serrated papers, with "tractor feed" strips on side. Have superior strength and printing surface to ledger papers.

White Ledger (WL). White, groundwood-free printing and writing papers such as copier paper, laser printer paper, white lined tablet paper, and stationary.

Sorted Office Paper (SOP). A selective mixture of papers typically generated in offices, comprised primarily of white ledger but including colored ledger, carbonless forms, envelopes, and groundwood-free coated paper. (Note: The term "sorted" is based on the fact that the acceptable mixture of papers must still be sorted from nonacceptable papers such as boxboard, cardboard, newspapers, magazines, and catalogs.)

Mixed Paper

An extremely broad mixture of papers, with few unacceptable paper types. Includes virtually all types of paper generated in offices, and a large percentage of papers generated in homes. Unacceptable paper types typically include plastic-coated papers such as frozen food packages and paper towels/tissue.

Old Newspaper (ONP)

Newspapers and other uncoated, unbound groundwood papers such as advertising fliers, election guides, and tax forms.

Phone Books

*This information provided by the Integrated Waste Management Board
http://www.ciwmb.ca.gov/Markets/StatusRpts/Paper.htm#Introduction